So, the vast majority of every day administrative command line utilities for Linux use -v as the switch for verbose…. when you use -v you EXPECT verbose. Well sometimes you get that one package which just CANNOT follow the rules. Someone has to think outside the box, someone has to be a unique snowflake. That someone should not be a mass process killing utility! whoever thought up that the argument -v to pkill should INVERT THE MATCH should really take a long slow look at how important being unique really is… because if you’re not aware of this, and you run something like pkill -9 -v nagios…. as root… it’s not going to do what you expect. Nothing good comes of that command.
This has been a PSA
grep uses -v as an invert-match switch as well. Just need to mentally associate pkill with grep, which isn't so large of a leap since pgrep comes as a part of the same process management package… still… frustrating to kill every process on the system BUT the one(s) you meant.